In a direct-current motor used as a driving source of an actuator, its performance degrades when the temperature of coils thereof rises due to the passage of currents through the coils. For this reason, conventionally, an independent temperature sensor is disposed in the direct-current motor, to detect the temperature (for example, refer to Patent Literature 1), or the coil temperature is estimated on the basis of the currents passing through the coils and the time period during which the currents pass through the coils, to limit the current passing through the direct-current motor on the basis of the temperature, thereby preventing performance degradation.